1. Field of the Invention
The present invention relates to erosion and sediment control for inlet grates, and more particularly to above grate based inlet filter systems for erosion and sediment control.
2. Background Information
The present invention relates to erosion and sediment control filtration system and method finding particular utility in reducing the amount of silt, sedimentation and debris in water entering storm drains via the grate inlets.
In response to tighter guidelines imposed by the federal Environmental Protection Agency (EPA) under the Clean Water Act, additional regulatory attention is being focused on controlling silt and sediment found in storm, construction site and other sources of water runoff. Various federal and state agencies have issued mandates and developed guidelines regarding the prevention of non-point source pollution. These mandates affect water runoff from storms, construction sites, and other sources. Such laws and regulations have a significant impact on not only how runoff water may be channeled and diverted, but also on, for example, the ways that contractors can dispose of excess or unwanted water from constructions sites. With respect to construction sites, the EPA has a goal of having developers prevent eighty percent of general contaminants, such as unwanted, site-generated sediment, from entering inlet drains.
One conventional type of inlet drain protection is referenced as a filter bag or “silt sack”, which is generally shown in the Pennsylvania Department of Environmental Protection (PaDEP) manual reproduced in FIGS. 1A-D. The inlet drain 10 includes a grate 12 over a vault or box 14 leading to the drain pipe 16. The inlet drain 10 may also include an above grade curb opening 18 within a curb 20. The conventional silt sack includes a filter bag 22 supported on a frame 24 (generally rebar members) that are held in place by the grate 12 on the box 14. The curb opening 18 may be blocked by a compost filter sock 26 or sand bags. The bag 22 may include a restraining mechanism 28 (nylon rope) to prevent excessive expansion of the bag 22. Many jurisdictions require an additional curb 30 to be used for below grate bag 22 installations. Other representative examples of the these known drain filter bags, silt sacks or drain inserts is found in U.S. Pat. Nos. 5,575,925, 6,086,758, 6,093,314, 6,059,964, and 6,045,691, and 7,201,843, and 8,017,005.
The applicant, headquartered in Pennsylvania, is involved with erosion and sediment control for the construction industry and has repeatedly seen the challenges of using below grate silt sacks for inlet sediment containment in residential developments during build-out. One of the drawbacks to existing filter bag filtering devices is the time and effort of installing, cleaning and replacing the filter bag filtering systems. Further in such systems silt, sedimentation, mud and other debris can build up quickly, causing the filtering devices to clog. As clogging begins, water flow decreases, which leads to a back-up of excess, unfiltered water. Back-ups may create additional regulatory, environmental, aesthetic and structural problems. Many systems have circumvented back-up of excess water by providing by-pass overflow features; however, while an overflow feature solves the immediate problem, the overflow water remains unfiltered, thereby defeating the primary intent of the filtration device.
When a filtering device's capacity is reduced to the point that it no longer adequately functions, the filter must be removed and either be disposed of or cleaned. Filtration devices can be difficult and time consuming to remove. For example, when a filtration device is attached to the underside of an inlet grate 12, such as bags 22, sediment is collected underneath the grate 12. Thus to change or clean a filter, the inlet grate 12 must first be removed. Next, either the bag 22 must be removed (to be cleaned or disposed of) or the sediment must be removed from the bag 22. Removal of the bag 22 can be difficult, as it may have a large mass of sediment that is very heavy. In this case, removal is at least taxing and time-consuming, possibly cumbersome and may even require lifting machinery. If the bag 22 does not hold a large volume of sediment, then removal will be more easily accomplished, but such remediation also must be done more frequently. In addition to the constraints and problems associated with cleaning or changing a filtering bag 22, timing also creates a problem. Oftentimes, clogging of filtering devices occurs during periods of heavy water flow, such as seasonal or other flooding periods. This presents an immediate need for cleaning or replacing a filter bag 22 coupled with circumstances that make the task even more difficult, onerous, and time-consuming.
Some have attempted to address the deficiencies of the prior art with primarily above grate filter systems, (also may be references as above grade—but above grate is more accurate) such as disclosed in U.S. Pat. No. 7,481,921, which is incorporated herein by reference. The '921 patent teaches the use of a randomly aligned coir fiber filter member 40 formed preferably of two generally 1 inch high filtering segments secured to the grate 12 via a plurality of zip-tie or cable-tie members 42. This is generally shown in FIG. 2.
Coir is a natural fiber extracted from the husk of coconuts used in a variety of products such as floor mats, brushes, mattresses, etc. Specifically, coir is the fibrous material found between the hard, internal shell and the outer coat of a coconut. The '921 patent teaches a primary filter of portion having a described preferable density between “3 oz./sq. ft. (sic) and 4.5 oz./sq. ft. (sic)”, and a secondary filter of portion having a density preferably between “4 oz./sq. ft (sic) and 6 oz./sq. ft. (sic)”. The '498 patent, discussed below, has noted that “although the [921 patent] apparatus [40] succeeds in preventing the passage of sediment and small debris that would otherwise bypass the grating [12], it is likely that such a fibrous mat would need to be continuously cleaned and would quickly clog in high flow situations or if left untended for any significant period of time. Moreover, the [921 patent] apparatus [40] provides no method of filtering liquid contaminants, such as motor oil, that may commonly find their way to storm drains [10].” U.S. Patent Publication 2008-0296211, which is incorporated herein by reference, also teaches the use of a randomly aligned coir fiber filter member formed preferably of two generally 1 inch high filtering segments secured to the grate via a plurality of zip-tie or cable-tie members, and the '211 publication seems largely to follow the teachings of the '921 patent.
U.S. Pat. No. 8,043,498, which is incorporated herein by reference, discloses a curb inlet storm drain protector having: a first, top layer comprising a generally horizontal surface having a plurality of holes formed therein, and a plurality of substantially vertical projections emanating from said horizontal surface, wherein said holes allow passage of water vertically through said first layer, and wherein said vertical projections extend a height sufficient to prevent passage of debris across said top layer while permitting passage of water over said horizontal surface, thereby preventing the drain inlet from being clogged; a center layer composed of a screen or mesh having apertures of approximately one-eighth inch or greater in diameter; and a third layer composed of a felt material having hydrophobic properties; wherein said first, second and third layers are fastened together and act as a single barrier that is coextensively laid over said grate.
U.S. Pat. Nos. 8,051,568 and 8,216,453 disclose storm water grate cover for attaching over a storm water grate. The grate cover includes an expanded metal screen sized to fit over the storm water grate; a U-shaped edge trim having a plurality of barbs thereon; a high flow monofilament fabric filter sized to fit over the expanded metal screen and being attached to said expanded metal screen; and a plurality of bolts attaching the expanded metal screen and monofilament fabric filter to said storm water grate.
U.S. Patent Publications 2002-0130083 and U.S. Pat. No. 7,399,411 are also of interest in the above grate filter fields.
Accordingly, there exists a need for better devices, systems and methods for filtering sediment from water entering storm drains, specifically those which provide ease of installation; can be easily cleaned or changed, even during periodic flooding; prevent unwanted back-up of excess water; filter nearly all or all of the water that comes through the inlet; and are cost effective.